Skip serverless AI assistant knowledge base status tests on MKI (#205678)

## Summary

This PR skips the serverless API integration tests for Observability AI
assistant knowledge base status for MKI runs.

Details in #205677

Author: pheyos

x-pack/test_serverless/api_integration/test_suites/observability/ai_assistant/tests/knowledge_base/knowledge_base_status.spec.ts

@@ -24,6 +24,9 @@ export default function ApiTest({ getService }: FtrProviderContext) {
   const observabilityAIAssistantAPIClient = getService('observabilityAIAssistantAPIClient');
 
   describe('/internal/observability_ai_assistant/kb/status', function () {
+    // Fails on MKI: https://github.com/elastic/kibana/issues/205677
+    this.tags(['failsOnMKI']);
+
     before(async () => {
       await createKnowledgeBaseModel(ml);
       await observabilityAIAssistantAPIClient